As far as I know, this is untested in court for online documents. There is an argument that says that each HTTP request is an act of publication, thus updating the copyright date to that point in time. It's not a view I subscribe to personally.
Copyright is dated to first publication. Re-publication is irrelevant. Disney doesn't get to extend the copyright on Mickey Mouse by re-issuing steamboat Willy. They have to bribe politician for that.